Large diameter pipes are buried underground and normally are provided with a protective coating. At intervals, this protective coating must be removed and replaced. This is accomplished by progressively digging up the pipe and lifting it from the trench in which it is buried, at which time the pipe is externally cleaned and then recoated. A typical disclosure of such an operation is found in the patent to Hoffman, U.S. Pat. No. 4,603,519 granted Aug. 5, 1986. This patent also discloses a blast machine which travels along the pipe and cleans the pipe by way of blasts of abrasive particles. While it is understood that the Hoffman machine serves this purpose, it is quite bulky and very expensive.